Telegraph repeater



Aug. 19, 1952 w. T. REA 2,607,852

7 TELEGRAPH REPEATER Filed Nov. 30. 1949 2 SHEET -SHEET 1 FIG- TO OTHER I? LEADS REGEN. T/r.

TO OTHER 5 LEADS INVENTOR W. T. RE A MAN-6 B Vl g ac 'l A T TORNE V Aug. 19, 1952 w. 'r. REA

TELEGRAPH REPEATER 2 SHEETS-SHEET 2 Filed Nov. 30, 1949 h E E SEzS 53o E J l [u g 4 g.

.. R B); W. T. REA

ATTORNEY IN l/E N TO Patented Aug. 1 9, i952 TELEGRAPH REPEA TER" wummrqma, 'Manhasset, N; Y.,1assi"ghbr" 0 4Telephone L'Lahoi-atories; j. Inorparatea;

York,N. 'Y.,' 'acorporation ofNew York A iplication'Ndvemb'er a0, 1949, Serial No;-1's0,2'67

l 9 Claims. (Cl; 178 70) ates to 7 an improvement in m ridcohtrol circuits. 1 The prcvem np consists *essehtially {in an arrangement of telegraph-repeaters and-cQhtrbl circuits such as tofalcilitatetheestabhshiiient ofeitlier ahalfdupl huh'rebeaterconce damn; or ofa rundup l'ex "intefconfiectionthe Iatt'er between two ness m; t a t it A "object o ffth-e intention is to improve teIe graph repe'atersf-and arnofe sbeci'ficobjectis tO- edu' "'teiegranh liile f'wi'th an individua1"repei'terj' andcontroi ei-amuse arranged that the line may be connected with *a number of other lines similarly equipped into a hubct'jriritrau1 =r prage-hau duplex 'or may-'be'direct1y' connected ;pb- ;a'i1bmer single iiriefsi'rhilarly eq ibped; tof bq f'mit ithe-J'oi-nd'lines to function on a full dupleg basis, and no duplex control lea rezqiuired "bettt'ee'nthe Y point-at \Vhiczhfl the in rconnection'is 'ma'defand the control *circuit or -j;e legraphrepeater'to effectuate the conyersion betweezi' r1 1mup1ex arid full dunlek foiieifation. Among the I advantages "oi so -arra'rigirlifg te1e-' gr v rites; ar that every use so 'equipbed is available fuse in'either type 'ofservicejwhich seg e me ei ficient'use *r tl'i'e' ffacilities', and "ce' the lines which are "to "fu'nctio'n in v fco'n ctiorisfare 'ea'ch terminated individualrepea and control' circuits'they may befinterconiiected "a?serviceboardWithout-"the 30 an I necessity for adjustment ininuch the same ni'an- 4 neras are hub circuits. There are other ad- Yantages, for instance it would eliminate the non -uniiormity in the "cross-connections which wouldresult if control-circuits were used only for 'multilegged circuits, two-legged circuits being direct; connected. In additionsince the jacksin a jhub r epeater equipped witha control circuit are inserted in th drop leg on which ordinarily relatively low potentials are required to be impressed, because of the shortlo-cal'drop paths-the jacksfin the 'fullduple'x circuits equipped with individual-repeater andcontrol circuits would be sirnilarlyfarranged; which would eliminate the V necessity ior 'providing special high voltage-jacks 45 U in the service board for directl'y conn'ected twoiferei'r' legged circuits. r ingarip i-feature of the present invention is a tel'e- 9 8 graph line equipped with a repeater and control circuit which will permit its employment either as a spoke offa hub circuit concentration or as one of two" correspondin ter'rninations for lines which ma y be joined to afford full-duplex operation. 'Ihisan'd other featureswill become appar- "f ayild m n 'emrrom the following description when "read theriresent an aififiient;ti ili fir st id asribu",

nefifdwrlfttmfi nff i'il me? regenerative"repeatersar"intercorifieot mi-g or left-hand contacts depending upon whether the regenerative repeater is or is not. tobe, em-

played. The vertical connection maybe considered to be the common hub jAfnumber'of other individual receiving legs and a corresponding number of other sending legs, nine of each,

for instance, not shown, maybe connected to the common hub. Interconnecting the receiving and sending paths of the single repeater shown is a. network of resistances, dry rectifiers and a double-triodevacuum tube arranged in an improved fiip-flop control circuit. The, function of this interconnecting network is to control trans mission between the branches of the network in a manner to be described. Each of the other individual pairs of legs of the repeaters assumed to be connected into the hubcircuit concentration, not shown, will beinterconnected individually in the same manner by its own individual control circuit. Each receiving relay, such as relay 1 and eachsending relay such as relay [9 are associated with a telegraph line or loop.

The network is arranged in such manner. that signals incoming to any one of the circuits'from its individual receiving leg canbe repeated to all of the other circuits simultaneously. The network also includes means whereby signals incoming to a particular circuit from its associated individual receiving legwill not be repeated back over the associatedsending leg to the same line. The network includes also arrangements whereby if telegraph signals are being received over a particular receiving leg and-simultaneously signals are re'ceivedfrom a second receiving leg'connected to the hub, said signals will be impressed on all' sending legs connected to'the hub. 'The signals are received from'a particular line by'means of'a receiving relay, such as relay l, which 'actuatesanarmature between its upper or marking contact andlower or spacing contact in"res'pon'se'to impulses incoming from its associatedline' and impresed'on its winding; The armaturebf relay-l is connected through resistance 2, 'a dry'rectifier 3"an'd conductor. 4 'to junction point 5 of hub section 6 which is connected to thejun'ction'l' between're'sistances 8 and l9'which resistances'are connected in series between'positive batteryand ground. Other .receiving conductors similar to conductor 4-extend from junction 5 through similar receiving branches individually to other armatures of other rece'ivi'ng" relays similar to relay l. Section-B of the hub may beconnected alternatively directly through branch [0 or regenerative repeater II, and then through section [2 of the hub to the sending junction-l3,-to which all sending legs of all 'ci'rcuitsin' the hub -s'ystem are-connected. From junction l3 the sending leg of the individual circuit shown extends through conductor I4, resistance l5, junction I6 andresistance -l1 to the grid of vacuum tube triode 18. The cathode of triode i8 is connected through the -Wil'ldlrlg of sending relay IE] to ground and throughresistance to negative battery in parallel Positive batthrough'resistance 40 to parallel branches.

4 tery is connected through resistance 2| to the anode of triode l8.

The armature of receiving relay I is connected from junction 26 through resistance 22 to parallel branches. One branch extends through resistance 23 to ground. A second branch extends through resistance 24 to negative battery and a third branch :to the left-handvcathode of double triode 25. Positive battery is connected through resistance 38 to the left-hand anode of double triode 25. From junction 39 in the anode circuit of the left-hand triode 25 a circuit extends One branch connects to the grid of the right-hand triode of 'tube-25'and a second branch extends through' res'istance fl to negative battery. The

. cathode-of the right-hand triode of tube 25 is connected 'tothe junction between grounded resistance 42 and resistance 43 which is connected to negative battery. From junction 28 in receiving leg 4 a-path extends through resistance 3| to the grid of the left-hand triode of double triode 25. Junction 30- is connected through dry rectifier 32, terminal 35 and resistance 36 to positive battery. From terminal 35, between dry rectifier 32 and resistance 36, a pathextends to the anode of the right-hand triode of tube 25. From junction 45 between resistance 36 and the anode of the right-hand triode of tube 25 a path extends through resistance 46 and dry rectifier 49 tel-junction l fibetween resistances I5 and I1. Negative battery is connected through resistance 48 to junction 41 between resistance 46 and'dry rectifier'49.

As mentioned above,--a regenerative repeater may be connected betweensections-i and I2 of the hub by actuating switches 52 and 53 to the right as shown. The regenerative repeater may for instance be in accordance with that described in detail in Patent 2,105,173 to Walter J. Zenner et al., January 11,;1938, which patent -is made part of the present disclosure as though set forth fully herein. It is pointed out that when a regenerative repeater is used a delay is introduced by the regenerative repeater between the reception of any pulse over one of the receiving legs connected to junction 5 and-the retransmission of the pulse over the sending legs, such as leg l4, after regeneration I The; delay introduced is approximately equal in duration to one-half; the durationof a-stand'ard pulse length. '"Double-triode tube'25 and its associated connections asmentioned above arearranged herein as an'improved flip-flop control circuit. Generally speaking a flip-flop circuit is a vacuum tube circuit which may forv instance compriseessentially two individual triodes, or a double triode, having the input and output-circuits thereof mutually interconnected, so that when one'isconditioned to-conduct the otheris responsively prevented from conducting and vice versa. The modification. in the present circuit consists essen tially of g the introduction of the dry rectifier 32 into the I feedback-circuit interconnecting the anode of the .right-hand section-of the-double triode to the grid ofv the left-hand section. -The voltage conditions applied to the circuit including the dry .rectifier are such that underone condition the rectifier iseifective toopen the feedback circuit,- so that the voltage condition of the righthand anode-is not effective cto-controlthe grid of the left-hand triode..- Thiswill be explained more in detail hereinafter.. w The individual repeater which is-illustratedis h w -i hemar ine coeditbelothar are aegrege I, connected to the hub circuit areiinengageme'nt with their upper ormarlgingcontacts so that they,

are all connected to positive battery. j Positive potential will beapplied from the potentiometer comprising resistances} and 9 through the hub e j n 13 mend n .1egs;.sun,a .l If} the, regenerative repeater, is used; it will be assumed that the circuit through.itis 'arranged. forthe marking conditionso as. to impress posi-. tive ,-potentialfupon-. the junction [3.1 However,

the potential actually applied across the input cf the left-hand triode of each double triode 25when themarking condition prevails depends'upon'the condition of the flip-flop control circuit in each individual repeater: The manner in which this isperjformed will be described hereinafter; Itis' pointed out at this time, howeveiy 'that the flip flop control circuit is arranged sothat for one nd ti n B a s l k d-pqnd t oa. ;Xe cis'es no'effectiv'e iniluenceon its sending leg; If the, control circuit in an individua1 ..repeaterjisf unlocked, therefora'fland a marking '0 positive potential is applied immlth hub through the sending leg, such as conductor 1| 4, .to the grid of trio'de ill, the triode will conduct. and the e'llect of. the current flowing through the winding of relay ll'l'will cause its armature "tov 'erigag its upper or 'marking contactl While a spacings lg: nal is impressed on the hub, the hub will be made more negative, The grids'of all tubesin unlocked sending legs, "will be made more' negative than. their cathodes and1,these tubes ,will".cease' toicom duct. Under. this "condition the armatur'es of their respective sending, relays @will beiun'der the influence'of negative battery through.re sista'ncev 20 and the winding, of each such sending relay "to ground, actuating the armature of ,.each such sending relay to engage with its spacing contact.-

Before'describing the manner, in which the flipflopf control circuitoperates in detail tapew rm the cQnt fQl functions, there will first be presented.

ageneral ,descriptionof thej functionsit must perform to meet the v operating requirements.

Ordinarily, when the system is. inioperation,

only one receiving relayjsuchasrelay l,.in the.

receiving leg of some individual repeater, will transmit toward the. hub at anyone time, The flip-flop control circuit individual to each re;

peater in" the concentration other than the con trol circuit-in the individual repeater which'is at the time transmitting toward the hub; must be unlocked for this condition to permit the passage of the signals through its associated sending leg.

stations.- e t v In order to preventretransmissioncf the signals, incoming to the individual repeater which i assumed. to be at the-moment transmitting toward the. huh-back through the sending leg of the same individual repeater from which they are being received, the flip-flop control circuit in that repeater ,must. place a locking. condition on its respective triode, such as, triode l8,.to maintain its associated sending relay. such as relay 1 9 continuously., in the marking condition duringthe entire,- interval.thatvv its own individual receiving leaisreceivineand transmitting-towardslthe hub'w 6 u h..s seelsim esse pm t hub h t 12. 1- tieular sending -legwilltherefore have he, "if

ln the event that'the'sending'jlg clap ti repeater, which ;w'wi11 "can" repeat r N been receiving signals "through the hub .i om receiving leg of another repeater, whichwe will callrepeater No. .2, not shown, the flip-. 'fiop ico'ri', trolcircuit in repeater No.1 must be in theffiiri: locked condition to permitthe passage ofth's nals,v u If repeater No. 2 ceases to transmit si startsto transmit toward the hub, it is necessary that two control functions bep'erformed'. First} it is necessary that the flip-flop control circuit" inrepeater No.1 look its own sending legfin" sponse' to the signals generated infits pwn're'c v ing'leg to prevent retransmission of .j its own s nalsto its own line. Second, it isv necessary t the flip-flop control circuit in repeat rm; which repeater was last transmitting and'th fIip fiop control circuit associated with which. peater was therefore locked, .be unlocked so t the signals from th'e'receiving leg of repeater No; 1 may pass freely from the hub through the, send ingleg of repeaterNoil, ;j

It. is to be understood of course for thecondi tions assumed, that sincerepeat'er No. 2 Was'fthtj last ,to transmit, its associated flip-flop circuit" was the only one which was in the locked c'ond'i tion' when. repeater No. 1 started to transmit.

Therefore, the flip-flop control circuits in al otherrepeaters willb'e in the unlocked condition. at this time and will beand will remain unafiectedwhen repeater. No.' 1 starts-to, trans m ilt,

There. is one other functional requirement'ofl the flip-flop control circuit. 'It must provide for. the condition under which, while one ,receigving leg, say that inrepeater No. 1, is transmitting: toward the hub, the receiving leg in another re peater, which we will call repeater No. 2,,starts to transmit toward the hub. Under suchcirsimultaneously, retransmitti'ng the signal over the connected lines to the distant connected cumstances, since it is impossible .to transmit communication signals effectively from more than one individual repeater through the single, I

hub to all of the other 'sendinglegs isimul'tane-q. ously, in order that the parties connected to'all lines connected into the concentrationbeinade'l aware of the attempted double transmission, .the'

control circuits are arranged so that .they'aref.

ing the sending relays associated with-the two} receiving legs which are transmitting simultaneously,- are operated to the spacing condition- The reception-of spacing signals at each-of the; stations which is simultaneously transmitting; 7

serves as, an indication of the double trans mitting condition since under normal conditions a marking signal exists on the sending of a station while it is transmitting.

It will now be assumed that the system been idle for an interval.

leg

has 1 Under 7 this condition the flip-flop control circuit in the particular repeater which was the last to transmit toward;

the hub will 'be in the locked condition, and the, control circuits in all other repeaters ,in the system; will be unlocked, It will; be; assun ied that a particular repeater, say repeater A, we shown,. starts to transmit-throughits receiving branch such as branch 4 toward the hub effect-of this on-all repeaters except-repeater A;

d it .eontr c r it w ch .w l b seaside reiee ien wil w.- e .'9 .i. Q1.1.. In response to the first spacing signal mltt i fre ithe receiVing-iegof; repe ter a tog ward 'the hub the-junction E and all receiving branches-or an repeaters connected to it, 111- eluding the repeater which last transmitted, are mademore. negative. The grids of theleft-hand triodes of all control circuits in the repeaters other than 'repeater Aare made negative with respect'tot heir cathodes. Their 'left-hand trio'des are. thereforeall placed in the non-conducting condition. Since no current flows in, their outputgc irouits, the junctions 3,9 are in their more positive condition under which condition the grids of the right hand triodes are madeimore positive with respect to their respective "cathodesland the right-hand triodes conduct. When, current flows in the output circuitsof the right-hand triodes, junctions 45 are made. less positive and the upper terminals of dry rectifiers 4 9 are made so negative with respect tojunctions [6 that they become non-conducting; In such condition the flip-flop control circuits have no control over triodes 18 which are then controlled by conditions imposed by the hub on'sending legs [4.

Asa result of the conduction of the righthandtriodes 'of" double triodes 25 and a consequent lowering of the potentia1 of junctions 35. the potential at junction 30 and the potential" applied to the grids of the left-hand triodes are maintained more negative with respect to' their. cathodes. Rectifiers 32 conductfcr this condi tion. The magnitudes of the resistances and of thebattery voltages as well as the characteristics'of the double triodes are so chosen that, as communication continues; in response to positive swings due'to the succeeding marking con ditions on the'branches such as.4 of the re-. peaters under consideration, the negative change inpotential due-to the conduction oi the righthand triodes is dominant in its effect onthejpog; tential impressed between the grids and ;ath-- odes of the left-hand sectionsof double triodes; 25. As a result of this, once a control circuit in; arepeateris-unlocked, in response to the first spacing. signal impulse of normal communica tiontsignal trains, it remains unlocked, since it. s" a ct y an 'of the a n si n 1 pulses in the communication signal trains. fie] while communication continues, all of the control circuits in the repeaters other than that in, repeater A remain unlocked and the signals transmitted toward the sending hubpass freely: through their sending legs. 7 I V Y j,

The manner ;in which the control circuit in a; particular repeater operates to apply a locking condition to its own sending leg when it starts to transmit toward the hub while all other repeaters remain in their marking condition will now be described. V 1

When the armature of the receiving relay such top terminal of resistance 22. A less negative potentialexists at junction 28 which-i applied through resistance 3| t the grid of the left hand "triode. The grid of the left-hand triode is therefore more positive than its cathode and the left-hand triode conducts. This in'turn cuts off -theright-hand triode, making the potential appliedthroughresistance-46 and rectifier 49 sufficiently po'sitive so that the grid of triode I8 is made more positive than its cathode and triode I8 is maintained in th conducting condition in turn maintainingrelay' I9-in the marking-condi- 1 tion.

. as relay l is first actuated to its spacing contact, full negative potential is applied directly to the Thespacing signal-on the receivin'ghub causes. the potential of junction 30' and of the grid of the left-hand triode to swing sufficiently nega-' tive that-rectifier 3'2 ceases to conduct even if the right hand triode were in a conducting c'onditionvat .the time the negative swin occurred. Hence the feedback path from the plate of the right-hand triode .to the grid ofthe leftehand' triode is efiectively opened at this time. j]:

, When the armature of relay l, in therepeater. which is assumed to be transmitting toward the hub, returns]. to the marking condition in re-. sponse to the marking signal impulses in the. communication signal .train, the grid of the left-. hand triode will be maintained more positive than its cathode. so that the locking condition applied .to.its sending legwill be maintained and the. sending leg will be unafiected by communi-. cation signal impulses impressed onit from the; hub. Therefore communication signals originating in the receiving leg of any repeatervcana not vbe repeated back over its own,sending leg.

When the receiving leg of one repeater istransmitting toward the hub and the receivinglegof. a second repeater starts totransmit toward the.

hub also, the hub will be made more negative than when apsingle spacing signal is impressed on it. Under, this condition the potential of the grids of all of the leitrhand triodes will be neg- This will,

ative with respect to thehir cathodes. unlock every control circuit andv a Spacingsignal will betransmitted from the huboVer the. sending'jlefgs' of all repeaters in the system, in-r} clu'ding the two which. are transmitting simul-i. taneously toward the hub,v the sendinglegs of which two repeaters would ordinarily. be in the, marking condition if but one were transmitting. L This serves as an indication of theattempted,

double transmission. 7 Attention is particularly fier 32 were not used, the ratioof the resistances couplingthegrid of. the left-hand triodeof doubleftriode 25Kto the receiving hub and to the, plate of the right-hand triode would be required. to be such as to produce a maximum voltagej swing atthe grid of the left-hand triodewhen:

, 1. The right-hand triode..changes from the. locked to the unlocked condition witha marking signal on thereceiving hub;

2. The right-handtriode changes un lockedv to the'locked condition with the receiv-- mg hub changing simultaneously from the spaceto the doublespace condition.

As the resistance ratio is changed, one ofthese swings will increase and the other decreasa- Hence the maximum swing would be obtained at a resistance ratio making the two swings equal. The magnitude of the maximum swing obtainable would, howev.er;-be too small to be practicable for. overriding voltage and resistanc variations.

When the rectifier 32 is employed, it presentsa low. resistance during the marking condition on the receiving hub. The resistance ratio. is then such asv to. place the voltage applied to the grid of the left-hand triode close to that of the.

plate of the right-hand triode. so that it is greatly affected by the plate swing. .When the receiving the voltage swing of the receiving hub for -the space and double-space conditions. As a result 1 directed t6 the hind. tron performed by the dry rectifier. 32, .If rectie,

Resistance Number Resistance Magnitude 2,000 ohms. 18,000 ohms.

18,000'ohms. 2 megohms. 2megohms. 17.000 ohms. 2,500 ohms. 6,000 ohms. 6,400 ohms. 32,000 ohms. '2 megohms. 0.2 megohm. 0.5 megohm. 3.2 megohms. 2.4 megohms. 2,800 ohms. 7,100 ohms. .56 megiohm. 1.6 megohms.

Refer new to Fig. 2. In this control circuit the principle of the increased voltage swing obtainable through the incorporation of a dryrec t'i'fier in the'interconnection of the feedback and gfid cifcuits of- (m of the tubes of a fiip -flop control 'circuit is' further extendedby the addi-- tion of the dry rectifier 50. The dry rectifier 50 is'so poledas to present a high resistance when positive battery is applied to the receiving-hub for the marking condition and a low resistance for the space and double-space condition. *By this means the grid of the left-hand 'triodeis in effect moved very near to the=receiving'hub for the lattenco'ndition. Thus'a further improvement in the magnitude of the grid. swing results.

'Assumingthe resistance and potential values of the foregoing as a representative operable set, the following table shows the' potentials --indidated 'for the" various conditions in Fig; 2.

mogene icolumn shows the conditions that exist when relay I: is markingythe hub is marking and th'elocking circuit"isreleased.' When relay'l goes spacing the instantaneous conditions be-'- come ass'shown;in-.-ico1umn -V. It will be noted that; theseareunstable; since although the locking circuit is 'assumedreleased,- the grid voltage ofthe' righte'hand triode withfrespect to its catl'iodeis negative. The circuit; -therefore,-- changes instantly to-the stable condition shown'in column I3-With-the-lockin circuit?held. g L: f

When" now some: other] receiving: leg? becomes spacin the --hubwill assume the "double' spa'ce condition and-the instantaneous conditions will become as shown in" column- VII." This i 'condiT- ti'onis-unstable because although the-locking circuit is assumed heldrthe grid voltage+of the right-hand triode 'withrespect .to its cathode is positive; The circuit; therefore, changes instantly to thestablecondition shown in" column VIII with-the*lockingcircuit released.

The minimum grid-to-cathode potentialiswin'gs afforded by the arrangement of 'Fig; 1 which the single rectifier is employed isan' 'improvement over a circuit which 'does 'n'o't em'ply the rectifier. -Theminimum gridto-cathode po't'em tial swings afforded by the arrangementof Figi 2 employing two rectifie'rs;- 'as indicated bythe above table, are substantialandrepresent-a fur; ther improvementtover" that obta'inable 'by "tfie arrangement inFig; '11 v j}; --Refer now" td-Fig'. 3 wh1fch shows two ip ter and control circuits identicaliwith bffteigs z hei'ein, eizcept thatthe hub pdtezitibifietr re; pla'cedby" afsing-le resistance RH; nected from a 'positive battery of namely- 10w p otential to the hub; It is to b'e ministe ia that whenfa half-duplex"concentration is to be armed a v bert of' oth'er such repeaters are uice to the same hubin the same'mahfir." :This is ind te by' 'thespur br strapeic'tending from there iv ing i hub RH, and the ending pffit "w en generative' repeater ll. Howevergwh'enfthe two repeater 1 and c'on'ti'o1 circuits are connected] to vbzmge conditions m Fig. 2];

' ifiesa estmmcannon. v

the foregoing table column I shows the con fo'rm' a full-duplex'circuit 'no otn'efiepeafieijaii ditions that exist when-relay I is. marking, the hub is marking and the lockingcircuit is held. .When'the hub goesspacing the instaneous conditionsbecomeas' shown in column II. Itwill be noted that thesezare, unstable. since, although theqlocking circuitvis assumedh'eld the gridvoltage ofthe: :rightehand 'triode 'with respect to its cathode-tiexpositive The circuit, "therefore? changes -instant1y.-toi-the stablecond on' shown in: column 1 III with: the- "locking di'ifCl-Iii? r'la ld control circuits'=-may" be connected" and theflar rangement is operative only when a regenerative repeater is not employed; "The manner in which the half-duplexiconcentration operates should be apparent ,from tlie foregoing description of the operation of the are rangementsofFigs.'1 and"2. I g e v u 'For 'afull-duplex circuit in which two repeate'rl and. control c'ircuitsare coupled togethef"atten-- tion is ca lled tot-hefact that'whena singlespaczhs'explai'nedin'the description of the 'ope'rationloffthe': circuit per :Figti an'd Fig. 2 in the foregoing, when two spacingsignals or portions of them exist on-the hub simultaneously,' both -con'- trol .icircuitslare unlocked t transmit spacing signals back the 'stations at whichfthey are 10 originating. Inth'it' cas'e" the reception of the "spacing? signals when the' in'coming circuit should maintained: in -:the marking conditionj serves as an'indicationbfian'abnorrnal conditionf-nam'ely the?attemptedtfansmission'of 'a plurality-of sign-als' 2 simultaneously through? a half-duplex h'ub concentration bompI'i smg mOi'e "than twofc-ir zcuits:which-"wouldt'cause mutilation of the signal elements; In .-the present full duplex arrange"- mentrhowever 'whenfonlytwo' cirfcuits are interconnectedfandtizvheii'v no' regenerative repeateris I employed; :there scan..- be no ifiutilation- 'azidthe received? signals '.can be' effectiv el yemployedfor oommpnication. 11. l

:TIThQlQYiefl-ZpDiD-g fc-po'rtion's oi signal elenient's causes e jozdiflieultyias canzbe nderstood fro'rn :th ifiollowinaiwi "'11: r 15 3 .1; ;;Let it Joe; assumed; thatzoth'e system is marking and that (3th? stqre'ceive rel'ay last transmitted toward the hub: f-Ihe w'estcontrol circuitis locked so that the west send relayiisrheldrmarking. east c ontrol 'circuitis gunlocked. s that the e lei' rp llat dein $116iWBS13T1g might e i h q h t iei eas i e d n 'l.e ow t t-be assumed-that-the -ea eceivingmelay i'eei es'.a spacing signalelemen T is -locks the east; control- ;cireuit;andthe'east sending leg. T It mocks the west control circuit and the-west sending-leg and it will be assumed 'that'TtHB 'sig na .is, ,passing through A r the we st sending" leg. Whil his condition -exists,-an'd after- :the 5 first portion et the.- signal- -has been "transmitted F fbU h the west leg let it -be assumed that "a pa ga is -e Yd:b :the:-west receive relay WRiLJIfhiS prducesthe double-space c'ondi- 4 ii nlwh cl tsise.z ng-: Of -bQth' sending less; Tlwestleg s alreadyr-opem andit remains open: "The locked east sending leg is opened so that a spacing signal element will exist on botli sending legs. After the terminationb'fthe re ception of the spacing signal element by *th east receive relay ER thefdoublg-spac e condition will be terminated. A single-space condition will signal in passing through "the regenerative 'r'e. peaterfis't delayed" for an interval "equal in duration to the duration of one-half a signal element so that the best portion of the incoming signal may be sensed. Then the regenerative repeater is' locked in' the determinedcondition for'the duration of a full si nal element. This signal element is passed on to the west sending leg. Now let it be assumedithatwhile this singlespace condition exists and about the time that the spacing signal received from' the east appears on the west sending leg, a spacing signal isreceived by the west receive relay. A double-space condition will exist on the receiving hub. Both control circuits will be unlocked. The latterpor-v tion of the spacing signal incoming from the east will be properly directed to the west'and will also 'be'misdirected to the east-from which it originated followed by the spacing signal from the west which will exist for a normal interval. The spacing signal received by the east will be unduly lengthened assuming that the signals overlap, c v The arrangement per Fig. 4 is operable when two repeater and controlcircuits are interconnected to formfa full-duplex circuit whether or not a regenerative repeater is employed.

7 Refer now to Fig. 4. In the arrangement per Fig.4, the; connections for the h alf duplei cork centration and for the two circuit full-duplex system 1 differ and switches swl SWZE'SWS and SW i are: provided to yef f ect thechange. flihe Switches may k a slu of erms in l in ads an plugs, bu a eill sraed .mrtne r simplest f orm; as two-position manually operable v key switches.;.. These switches whengin the pos i:- tionsshownin Fig. A -interconnect their respec tive repeaterrand --con tro=1* circuits into a halfduplexconcentration. which may be comprised of three-or .more. repeater and. control circuits; The receiving hubL-BH and the sending hub SH may lb e g interconnected directly or through .7 a regenerator vand thea-halieduplex concentration W er te th an er 2 d s r d .f r -=-..th operation oi Figs. 11 and; and the half-duplex concentration per-'F, ig.3... ..-z=,

When the gswitchesi SVH SW2: SW3 and am per. Fig. .4 are in theiralternate positions, a full incoming spacing signal 'element from the west receive relay WR. The-west controljcircuit will'r'i' i function to lock the west send leg. Theeastnom 1.

trol circuit will remain ;u-nlock edwhile the latterI portion of the spacing signal incoming froni re x a lay WR passes throughythe east sendinglefg: 7

It is not possible tojoperatefifull d-I 1 wit the circuit arrangementof Fig.- .3 when a r'egen-" erator is employed because oi-the-delay-introduced by the regenerative repeater. The control legs ofthe two repeatersrsothat a;

91%??? n fienalmos zin tantaneaus m Wgth M 5115: r sponse; itOfzhe :sin l 3. 1 7; .Pe q qn fi finsappearing on the; re ceiving hub. Also a singlejegeneratoricannoti simultaneously v.1regenerat .two'. :Amcorrelated thezeast. QQPE I L rw iri ae i as mmedia ly ck:the ridle'g "Theywest'controlcircui unctions.

duplex'system interconnecting two repeater and 'contr'olcircuit'sonly isestablished and the system is operable whether or not regenerative repeaters v are'einployed; iIt'will be observed that the connections for the full-duplex system per-Fig. 4; exist in response to the latter portion pr the stilli ff.

differ" from thos of" the half-duplex concentra-. tion per Fig.4 in a numberoffrespects. 7 the full-duplex" arrangement there common hubs Second. the receiving ='leg. control 'circuit'in the-full duplex arrangement is connectedfto the sending'legpf theother control circuit. ,filiird ln the in] x V, lea arrangement; when required, a regenerativerepeater is in sertedi in'each'individual interconnection-b tw enthe eiege'ri; erator cannot serve the system as n the halfduplexrl-honcentration' arrangeine .ZQHOWBVGF; the most -iniportar'it --dfierenc tween: the -halr-dupleiz c'oncentra udn" a; full duplex arrangement of; -Fig i i is' th'a' in full duplex arrangementqa irsistanc nected' from theareceiving vhubpoten tial source; to -what; correspionds eto the receiving" hub and will .be called hereinafter the:ireceiving verteiif and. a. second; resistance-R2 hasfo'ne terminal coir-i matted directly ojth'e; receiving'zvertex an'd-- a;'

' anally: arranged,-\ however',-,ior: halt -duplex opera- .FFr'onrQthe oregoing p, v,

g m l-Re an}; fWhatisfcl'airned say; I f" it hub telegrapl'ilrepeater ha cr m e e f le e bn el; ne'cting; said-legs"for locl zingfandunlockin s i e res ns rid- Ls e1i e"= tidns -impressedfonsaid receiving leg a c i s-w iiulb -1 i e trei e e'cni e m s e .en cc i i t s nded ei x, t n ti o e d rce te e con ol: ci c and a .switch-i-ntermedi p} said-repeater and con;- t FOl circuit-and -saidfirst terminationand said second-:termination-,-;=to permit-theconnectiom-oi said --repeater-'andg control circuit to=-=-s aid --first t'errninationor to-isaidfisec'ond terminationa V v 2.:A-telegraph1.repeaterf and control circi iwa first half -;duplexhub concentration termination, N aqsecond =--full-duplex termination, a switch ior 9W Q 5. W .h emcee f interconnecting said repeater andcontrol circuit t zersce icg icx z ei clfic i to=- saidfirst-or +'said--second terminationsiva;

r en 11 8 dpuble space gentr 1 in. said ..control i j t .1851 a g twill-pass he dou-bleespace cor imoirespofnsive tothe imposition psendipgle i e ,trepe t -w -11. femellyvcr rfcrrt ar insfice di-tio 'of' bc the "east and West repeaters;.; there-':- is -noi-?hold applied to eithefsending leg so that a spacing. signal originating in either will pass freely', through the sent-ro ues th' 'o'ther. As nortion a control circuit in aparticulan repeagterlocks its individual sending-deg when its individual rec'eivihg'legtraii's'fiiit's' afs'ig'rfaltowardthe hub tofiprevent the transmission of the received .signal baclilto itssource; is no possibility of this misdirection-ofsignalsiri the mn' aup ex arrangement pen-Eigad astth'erreceiving leg of a particular repeater is separated from the sendi'ng .regtr the same ,mpe er'since there'"s" :1-1'10 singie comfiibn-hus wwrficrreacii is can tr ed. Thecomplete separation of the receiving: and second potentiometer, said first potentiometer sending legs of each repeater permits the con'di comprising a first resistance element connected tioning of the control circuit so that th sending in series with said receiving leg of said first releg of a repeater is never locked. It is unlocked h a r nd to sa d first c nn cti n, and a second for a marking condition as explained. It is unf resistance element connected between the junclocked instead of locked in response to a single tion of said first resistance element and said first space so that it is in condition at all time to connection and a source of potential, said second pass signals incoming from the opposite repeater. o io ter comprising a third resistance ele- Further the m t separation of t sending ment connected in series-with said receiving leg and receiving legs in each individual repeater and p of Said Second repeater d to id Second conmaintaining the sending legs always unlocked nection and a fourth resistance element conmakes it possible to insert aregenerative repeater nected between the junction of Said third cin either connection between the receiving and sistance element and said second connection and' sending legs for full-duplex operation. a Source of potential To effect this, as mentioned, each single space A System in accordance with claim 3 having is disguised as a double space by producing a m a first regenerative repeater in said first condouble-space voltage condition on th hub t nection and a second regenerative repeater .in deceive the connected control circuit. As a re- Said Second connectionsult of this deception, the full-duplex arrange- In a g 'op ystem, a eg ap ep ater ment per Fig. 4 has been aptly named, in the havmg a recelvmg leg and 8/ Sending a first art, the hoodwink circuit. 5 and a Second termination, a Switch. d Switch The relationship of t resistance values I operable to connect said repeater to said first or produce t double-space potential condition n to said second termination, a control circuit coma response t a single space in t fu11-dup1 x prising a potential-discriminating device conrangement per Fig. 4 are as follows. Rooting Said legs, on put c rcuit for said device It is assumed that the potentials of the potenincluding Potentiometers f discriminating betial sources in each system are the same. Then tween a first and Second p tential condition it is required that when a first or a second signal condition is imposed on said control circuit when said repeater R R +2R circuit is connected through said switch to said R3+Rg first termination, and potentiometer means in first resistance means-for impressing" a first p'o When said repeaters' are connected throughsai'd 1 bond ionin'iposed on said-second or 'sa moms;

said second termination for actuating said control circuit as for said second'signal condition by- 3? I p producing said second potential condition in re- 5? sponse to the imposition ofs'a'id- 'fir'st signal cbnint ne t t dition when said repeateris connected through said switch to said second termination. 6. In a telegraph system; affirst repeater, a first ontrol circuit cqnnectedto said repeater, a

peatrs" fir switc firstanda-second' termination selefc vely 'cqnnectahle to"'said repeater through h- A a' 's'econd repeater; aj second control v s fie d se nd a r iefi '0 swit ht a third termination, 's aid'first'or sam't-tfiird termination selectiveli connectable to second repeater through said second switch, said first and s'aid'sec'o'nd repeaters connectable through each of said terminations-potential and 1 ,tential and a second potentiaL' substantially dif ferent-froin said first potentialgion said control circuits in response to a SingIe-SpaCe-signaicondition :anda --doub1e-"space signal condition, respect'ively; imposed "on-said -first termination;

switches te -said first-termination and potential and second" resistance ineans for impressing'said scond potentiaion said firstoi said second'c'ontrio 'uit in response-to al sing1e-space 'signa1 ,7 Y thi'rd termination; ;-re'speetive1y,fwhen-Esaid repeaters are ic'onnected' through" j's'aid switchest0 said l a dfth rd" erm nat n r 11 ra i 't i p in qa first and a. second hub type repeater eachfhaving Th WWW in i m iv s -.1;e iamian irm v u file. 9W P sendin ":leg and interconnected b'etwe'n said M ieg ndivi dual potential-discriminating con-5 V trio c1rc'uit,i"said contror'circuits eachj havinga 509 I double s'paceiffeature'; jsai'dfeature'comprising 23235896, Jan 14 194i spacefdischafge' devices discriminating between potentials applied' theretojfor a single s'paceand a f doub1e' space signaling condition; said repeaters inte' connected; through a single common hub to FOREIGN PATENTS 'qr t iariiam 14:19:11 

